The present invention relates generally to a Light Emitting Diode (LED) driver and, more specifically, to a switching converter capable of a very high step-up ratio and offering High efficiency at high switching frequency.
Recent developments of light emitting diode (LED) backlights for LCD panel displays in laptops and monitors require driving large arrays of LEDs. In these types of LED arrays, the typical input voltage ranges between 9 and 20V, whereas the total forward voltage of the LED array can exceed 200V.
Common prior art solutions to drive large LED arrays is to use a boost voltage regulator followed by multiple linear current regulators, such that the LED array is broken into a number of LED strings. All of the LED strings are supplied from the output of the boost regulator in parallel. Corresponding linear regulators control the current in each string individually. Driving all LEDs in a single string is a less expensive approach since it requires less circuitry. However, a boost converter is typically quite inefficient at such a high step-up ratio, especially when operated at switching frequencies required to fit the small size constraints typical for LCD screen backlight units (BLU).
Therefore, it would be desirable to provide a circuit and method that overcomes the above problems. The circuit would be a switching converter capable of a very high step-up ratio and offering High efficiency at high switching frequency.